package main

import (
	"context"
	"errors"
	"reflect"
	"strings"
	"testing"

	"github.com/novox/mesh-controller/internal/link"
)

// recordingDelivery is a delivery that writes down what was done, in order, and fails where told.
type recordingDelivery struct {
	did        []string
	grantErr   error
	declareErr error
}

func (r *recordingDelivery) grant(_ context.Context, sending []readyNode) error {
	for _, s := range sending {
		r.did = append(r.did, "grant "+s.node)
	}
	return r.grantErr
}

func (r *recordingDelivery) declare(_ context.Context, s readyNode, _ []byte) (string, error) {
	if r.declareErr != nil {
		return "", r.declareErr
	}
	r.did = append(r.did, "declare "+s.node)
	return "digest-" + s.node, nil
}

func ready(names ...string) []readyNode {
	var out []readyNode
	for _, n := range names {
		out = append(out, readyNode{node: n, declared: sendable{Resources: []map[string]any{{"id": "x"}}}})
	}
	return out
}

// novox/hq issue 249: the grants that come with a module's new declarations are issued before any
// machine is sent the code that uses them — except the machine holding the bus, whose declaration
// carries the controller's own right to issue them, and goes first.
func TestGrantsAreIssuedBeforeTheDeclarations(t *testing.T) {
	d := &recordingDelivery{}
	digests, err := deliver(t.Context(), d, "", ready("anchor", "laptop"))
	if err != nil {
		t.Fatal(err)
	}
	want := []string{"grant anchor", "grant laptop", "declare anchor", "declare laptop"}
	if !reflect.DeepEqual(d.did, want) {
		t.Fatalf("delivered in the order %v, wanted %v", d.did, want)
	}
	if digests["anchor"] != "digest-anchor" || digests["laptop"] != "digest-laptop" {
		t.Fatalf("the digests sent were not answered: %v", digests)
	}

	held := &recordingDelivery{}
	if _, err := deliver(t.Context(), held, "broker", ready("broker", "anchor")); err != nil {
		t.Fatal(err)
	}
	want = []string{"declare broker", "grant broker", "grant anchor", "declare anchor"}
	if !reflect.DeepEqual(held.did, want) {
		t.Fatalf("with the bus's machine in the send: %v, wanted %v", held.did, want)
	}
}

// A grant that cannot be issued holds back the machines it concerns and is an error the caller
// retries on — never "until the next push" — and the bus's own machine is sent regardless, so the
// grant that would let the controller issue memberships is never held behind them.
func TestAGrantThatFailsHoldsBackWhatItConcerns(t *testing.T) {
	// A failure naming no machine (the buckets): everything but the bus's machine.
	d := &recordingDelivery{grantErr: errors.New("the bus refused the bucket")}
	_, err := deliver(t.Context(), d, "broker", ready("broker", "anchor", "laptop"))
	if err == nil || !errors.Is(err, errGrants) || !strings.Contains(err.Error(), "the bus refused the bucket") ||
		!strings.Contains(err.Error(), "anchor, laptop not sent") {
		t.Fatalf("a failed grant was not said as the send's failure: %v", err)
	}
	if want := []string{"declare broker", "grant broker", "grant anchor", "grant laptop"}; !reflect.DeepEqual(d.did, want) {
		t.Fatalf("delivered %v, wanted the bus's machine alone", d.did)
	}

	// A membership that failed for one machine: that machine alone.
	one := &recordingDelivery{grantErr: &grantsRefused{nodes: map[string]error{"laptop": errors.New("no")}}}
	_, err = deliver(t.Context(), one, "", ready("anchor", "laptop"))
	if !errors.Is(err, errGrants) || !strings.Contains(err.Error(), "laptop not sent") {
		t.Fatalf("one machine's refused membership was not said: %v", err)
	}
	if want := []string{"grant anchor", "grant laptop", "declare anchor"}; !reflect.DeepEqual(one.did, want) {
		t.Fatalf("delivered %v, wanted anchor sent and laptop held back", one.did)
	}

	// The announced upgrade that hit it is asked again.
	if !errors.Is(askAgainOnGrants(err), link.ErrTryAgain) {
		t.Fatal("an announcement whose send stopped at its grants is not asked again")
	}
	if other := errors.New("laptop could not be resolved"); errors.Is(askAgainOnGrants(other), link.ErrTryAgain) {
		t.Fatal("any failure is asked again, not only a grant's")
	}

	// Nothing to send is nothing granted either.
	none := &recordingDelivery{grantErr: errors.New("never asked")}
	if _, err := deliver(t.Context(), none, "", nil); err != nil || len(none.did) != 0 {
		t.Fatalf("an empty send granted or failed: %v %v", none.did, err)
	}
}

// Whether the bus's machine goes first is read from the user list alone, by its digest.
func TestTheBusMachineIsBehindByItsUserListAlone(t *testing.T) {
	list := "users: [a, b]"
	if userListBehind(list, digestOf([]byte(list))) {
		t.Fatal("the list it was sent reads as behind")
	}
	if !userListBehind(list, digestOf([]byte("users: [a]"))) || !userListBehind(list, "") {
		t.Fatal("a changed or never-sent list reads as current")
	}
	if userListBehind("", "") {
		t.Fatal("a machine sent no list reads as behind")
	}
}

// The machine holding the bus goes first: its declaration carries the user list the new grants are
// checked against. Among the machines it is moved to the front; not among them it is added only
// when it is behind.
func TestTheMachineHoldingTheBusIsSentFirst(t *testing.T) {
	for _, c := range []struct {
		what   string
		names  []string
		holder string
		behind bool
		want   []string
	}{
		{"among them", []string{"ace", "g14", "novox"}, "novox", false, []string{"novox", "ace", "g14"}},
		{"not among them, behind", []string{"ace", "g14"}, "novox", true, []string{"novox", "ace", "g14"}},
		{"not among them, current", []string{"ace", "g14"}, "novox", false, []string{"ace", "g14"}},
		{"nothing holds the bus", []string{"ace", "g14"}, "", true, []string{"ace", "g14"}},
		{"only it", []string{"novox"}, "novox", false, []string{"novox"}},
	} {
		if got := brokerFirst(c.names, c.holder, c.behind); !reflect.DeepEqual(got, c.want) {
			t.Errorf("%s: sent in the order %v, wanted %v", c.what, got, c.want)
		}
	}
}